Fuse



E F. KlEFER Dec. 25, 1934.

PUSE

Filed Dec.

III/III l '/z/////////////// z.

INVENTOR ATTORNEYS.

Patentd Dec. 25, 1934 PATENT OFFICE FUSE Edwin F. Kiefer, Cleveland, Ohio, assignor to National carbon Company, Inc., a. corporation of New York Application December 1, 1931, Serial No. 578347 18 Claims.

The invention is a delayed action fuse for electric circuits.

One object is to provide a fuse that will carry a large overload for a shortperiod of time but will ?low on a small overload after a longer period of Another objectis to provide a. fuse that will minimize the arc formed when it blows.

Another object is to provide a fuse that will not deteriorate with age or use.

Other objects are to provide a fuse that is compact, reliable, low in cost, easy to manufacture, and positive in action.

Other aims, objects, and novel features will be manifest by the following specication and the accompanying drawing, of which:

Fig. 1 is a vertical section through my fuse installed in a plug mounting, and

Fig. 2 is a longitudinal section of my fuse installed in a cartridge mounting.

My tuse comprises two pieces of electrically conductive carbon, such as carbon rod, held together by a joint oi fusible alloy. The carbon r'od is preferably cylindrical and the joint is preferably between the ends.

The Iusible alloy may be ordinary solder composed of a mixture of substantially equal parts of lead and tin or it may be any other similar or equivalent alloy adapted for the purpose. Preferably the fuse is provided with means, such as a spring, to separate the carbon sections when the i'usible joint therebetween has melted, and this spring may carry the electric current to the fuse, or a separate conductor may be provided to carry either all or part of the current. The fuse may be mounted in any suitable holder, such as a plug or cartridge, or it may be mounted directly upon some portion of the apparatus it is adapted to protect.

One example of my invention as installed in a !use plug is shown in Fig. 1. The plug comprises a dielectrlc body 10 of any suitable material, such as porcelain or bakelite, having an axial opening 11 therethrough closed at the top by a transparent window 12 carried by a supporting frame 13 and closed at the bottom by a conical dielectric tip 14 held to the body 10 by a threaded metal or conductive shell 15 forming one terminal of the ruse; Secured to the center of the conical tip 14 is a conductive metal holder 16 forming the other terminal of the ruse plug, and a conductive separating spring 17 is attached to the outer edge of the metal shell 15 by a joint of solder or compression and extends inward through the body 10.

.A ruse 18, comprisin'g a cylindrical-carbon rod 19 having one end thereof joined directly to one end of a similar rod 20 by a joint of solder 21 in contact with both rods, is mounted under tension between the inner end of the separating spring 17 and the metal holder 16. The carbon rods 19 and 5 20 may be attached to the spring 17 and metal holder 16 by any suitable means, such as a joint of solder or compression.

Another example of my invention 'installed in a cartridge fuse is shown in Fig. 2. The cartridge comprises a tubular dielectrlc body 22 of any suitable material, such as fiber or bakelte. A conductive metal cap 23 is mounted upon one end of body 22 by a th'eaded or compression joint 24 and a similar cap 25 is mounted upon the other end of the body 22 in a similar manner.

A conductive separating spring 26 is Secured to the inner side of cap 25 by suitable means, such as a joint of solder 27, and my improved fuse comprises a carbon rod 28 having one end thereof directly joined to one end of carbon rod 29 by a joint of solder 30 which is mounted under tension between the inner end oli separating spring 26 and conductive cap 23. The fuse'may be secured to the cap`23 by any suitable means, such as a joint of solder 31'-and it may be secured to the separating spring 26 by a similar joint 32. The separating spring 26 may carry the entire current passing between caps 23 and 25 through the fuse or a separate conductor 33 may be provided between rod 29 and cap 25 to carry a part of the current.

When in use the fuse plug or fuse cartridge may be held by a suitable fuse block or other mounting well known in the art and ordinarily used with fuses of the form shown. When in use the electric current passes from one terminal to the other through my fuse and when the fuse is sulciently overloaded the heat generated by the passage of electric current through the carbon rods melts the joint of fusible alloy or solder by which they are joined, and the separating spring draws them apart. As the arciormed at the time of separation is between the carbon rods-it will be minimized as this is one of the characteristics of the carbon.

My ruse is entirely different from and possesses many advantages over thermal cut-outs or relays having contacts that are opened by heat generated in a. coil of wire having high resistance, and "Sneak" fuses in which a piece of fuse wire is melted by heat generated by the passage of current through a coil of high resistance wire. As my ruse has a lower resistance it consumes less current during normal operation, and as the lifi circuit is opened by the rapid separation oi carbon Contacts, the trouble causecl by arcing is much less than in thermal relays.

In Sneak fuses and to some extent in all uses employing an exposed piece of usible alloy wire, this wire may, after being in use ior some time, become covered with a coating of oxide that has suicient strength to support the fusible metal after it has melted se that it will carry current in excess of that at which it is suppeseci to blow. In my fuse the fusible alloy is protected by the carbon rods se that it cannot cleterierate or exidice with age or use. Thereere my hise is more reliable and positive in action than uses em= ployng bare use wire.

The reliability and desirable characteristics oi my fese are shown by the results obtained from those tested. Fer instance, it was found that nses adaptecl to carry 4 amperes continuously would blow on a current of 5 eemperes after a pe= riod of 2 minutes, while on the other hand, these iises would carry from 2 to e times their normal load for a period of lo to 20 seconds. These resuts show that this fese is especially adaptecl te protect electrical apparatvs having inductive windings, such as motors, as it is well known that such devices reqnire a large overloaol :Zor a short period of time when started, but areliable to be injured by a small overloacl ever along period of time.

'While i have shown my fuse as having two car hon rods joinecl by a `fusible alloy and instfllecl in conventional mounts, it is unclerstoecl that the fese may have other forms and be mountecl in different ways. Although the carbon elements of the use are shown joinecl end to end, the car bon may have other forms. Furthermore, the area of solde'r joint between the sections may be varied; to vary the characteristic oi the fuse.

Where no particular material has been men tioned it is understoocl that conventional material has been employed. whether the material has been mentioned or not, it is understoozi that similar and equivalent materials may be substitnteol. :it is also understoool that the general form, shane, and relative arrangement of the parts may be alterecl without departing from the spirit of the inventien or the scope of the clairns.

claimzi. f-i clelayeol action iuse comprising a clielectrio body; two conductive terminals mountecl on said body; a conductor spring carriecl by one of said terminals; and a fuse comprsng two pieces of carben red held together directly by a joint of fusible alloy, mounted under tension between said spring anol sai`other terminal.

2. A delayed action 'fuse cemprising two pieces of cylindrical carben red directly held together end to end by a joint oi' iusibie alloy; means ;for meunting said fese in a suitable holder; and, a spring in said holder for separating said carbon rods when said iisible alloy has been melted.

A delayecl action fuse comprising two carben rods held ,together directly 'by a joint of solder; means for meunting saicl fuse in a suitable hoicler; and means in said hololer i'or separating said car bon rods after said joint has `*neltect i. A delayecl action fese comprising two carbon reds held together 'by a usible joint; means i'or mounting saicl use in a suitable heider; a spring in said helder for separating said corben rods when said joint fases; ;and a conductor in parallel with 'said spring'.

- j. A delayed action'use comprising two carbon rods directly held. together by a joint aeaptco to be fused when said fuse is overloaded, and means for separating said corben rods when said joint fuses.

6. A delayed action use comprising two carbon rods directly held. together by a joint of selcler.

7. A fuse for electrical circuits, comprising two carbon elements directly joineci by a fusible alloy.

8. A delayed action fuse comprisng two ear leon elements directly joined by a usible joint and. meuntecl under tension.

9. A delayel action fuse comprising two car leon elements directly held together by a usible joint and means for maintaining said joint under tension.

io. A delayed action cemprising the com bination of two elements adaptecl to become heatcd; a joint adapted to be fuseel by said heat in contact with both of said elements, and. means for separating saicl elements when said joint fuses.

li. A delayeel action hise comprising the combination of two resistance elements adapted to become heated by the passage of electric current therethrough; a joint for holding said; elements together 'adapteo to be tosca by said hoat; and means for separating said elements when said joint fuses.

12. A delayeol action ruse comprising a hollow dielectric holcler; two cenluctive terminals mountecl on sam holder; a conductive spring carried by one oi* said terminals within said. holder; a fese comprising two cylinclrical carbon rods Secured; under tension in said helder in axial alignment between said spring: and ene of said terminais; and a iusihle alloy 'limited directly to one end of each of sale rools te secure them together.

13. A delayed action ruse comprising a dielectric holder having a cylindrical opening therein; a cylindrical fese in said holder in axial align ment withsaid opening cemprising two carben rods having substantially flat acljacent encis; a thin layer of fusible alloy united chrectly to the adjacent ends of said rods; and means i'er sup" partine sm'ci rods in said holder comprising a spring in said opening Secured uncl 'r tension to one of seie rods.

lt. A clelayeci action hise comprlsmg two car ben rods united by a joint of solder in contact directly there-viti a holder saicl fese; means for rnounting saic .fese in holcler; and means in said hololer i'or separating said when said solder fese&

15. A delayeol action rose cemprising a t'nslble element; two car'oen ros united directly by element; a holder having an opening therein; and means .tor mounting said carloon rods in saiol holcler compris ig a spring in said opening for separating said rocls when said element 'UL'SBS.

le. A clelayecl action hise comprising a cylin-= dricai dielectric heider having an aiziet cylindri cal opening therethrough; a conductive cap on each end of smet holder over each end of saiel opening; two cylindrical carhon rods in said holcl er in axial align' cnt with said opening; means or securing one oi saiel rocls to one of said caps; a fusible alloy united directly with adjacent ende of saicl rods; a concluctive helical spring in said holder in anial alignnent with said rods secrecl under tension between the o' r of said rods and 'the other of sai& capo; anti a fiexihle electrioai.

conductor in parallei with spring.

i i. A delayecl action fese comprising pleh' having a cyl'lnchical oielectric both; vath, e. cyhn drical opening therein; a, conductive holder extending through said body at the axis of said opening; two cylindrical carbon rods in said body in line along the axis of said opening; a fusible metal united directly with adjacent ends of said rods; means for securing one of said rods to said holder; a metal shell Secured to the outside of said body and covering a. portion thereof; and a fiat conductive spring extending laterally through the wall of said body with one end secured to said shell and one end Secured under tension to the other of said rods.

18. A delayed action fuse comprising two carbon rods and a fusible alloy united directly with each of said rods to secure them together by a. joint of adhesion.

EDWIN F. KIEFER. 

